1. Field of the Invention
This invention relates to a toothbrush, and more particularly to a toothbrush capable of exhibiting a high cleaning function sufficient to effectively remove hard to remove dental plaque which tends to readily accumulate at areas such as recesses between teeth, boundaries between teeth and gingivae and the like and capable of feeling soft to the gingivae to a degree sufficient to exhibit excellent usability.
2. Description of the Prior Art
In order to protect teeth and gingivae from periodontal diseases and dental caries, which are called the two major dental diseases, it is essential to remove dental plaque by means of a toothbrush. For this purpose, it has been recently recognized that cleaning of teeth which is carried out by using tips of the fillings of a toothbrush is effective for removing dental plaque, such a way of brushing being called scrubbing, the Bass technique or the like.
In a toothbrush using fillings made of a synthetic filament material, the fillings are each formed of a soft material into a thin shape in order to prevent tips of the fillings from damaging gingivae during cleaning by brushing such as the Bass technique or the like. Such fillings feel soft to a user, however, they fail to exhibit rigidity and/or stiffness sufficient to permit dental plaque to be effectively removed, as well as satisfactory durability.
Also, a toothbrush of another type is proposed, which is constructed in such a manner that tips at both ends of each of the fillings are each formed into a tapered shape so as to permit the tips of the fillings to enter or reach areas such as recesses between teeth, boundaries between teeth and gingivae, and the like. Unfortunately, a length of the tapered tips of the fillings thus provided is as small as about 1 mm, so that the toothbrush fails to significantly improve both a cleaning function and a soft feeling exhibited to a user thereof. Thus, the tapered tips of the fillings fail to exhibit advantages over conventional fillings of which the tips are rounded.
Further, it is known that fillings each having tips formed into a pointed tapered shape of an increased length by chemical treatment are used for various kinds of brushes such as painting brushes, cosmetic brushes, face washing brushes and the like, as taught in Japanese Utility Model Application Laid-Open Publications Nos. 12934/1982 and 65632/1982. In various kinds of brushes disclosed in each of the above Japanese publications, fillings of which the tips are each formed into a pointed tapered shape are used in place of conventional fillings exclusively made of natural animal hairs, to thereby improve feeling properties of the brush, its durability, its sanitary properties and the like. However, the toothbrush including the pointed tapered fillings is substantially inferior in cleaning performance to a conventional toothbrush having non-tapered fillings set thereon, because the tapered fillings are excessively soft or flexible owing to a improper tapered shape. In order to solve the problem, it is required to provide the fillings with suitable hardness by increasing a maximum diameter of the fillings. Unfortunately, this causes the pointed tapered tips of the fillings to be so hard to damage gingivae.